Azeotropic and azeotrope-like compositions of 1,1,2,2-tetrafluoroethane

ABSTRACT

The azeotropic compositions of 1,1,2,2-tetrafluoroethane and 1,1-difluoroethane and the azeotropic and azeotropic-like composition of 1,1,2,2-tetrafluoroethane and one of, 1-chloro-1,1-difluoroethane, perfluorocyclobutane, n-butane, isobutane and 1,1,1,2,3,3,3-heptafluoropropane, and their use as refrigerants, aerosol propellants and blowing agents for polymer foams, are disclosed. The azeotropic and azeotrope-like compositions of 1,1,1,2-tetrafluoroethane and one of perfluorocyclobutane and 1,1,1,2,3,3,3-heptafluoropropane are also useful as fire extinguishants.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application Ser. No. 07/837,416 filed Feb. 20, 1992, now abandoned, which is a division of 08/676,637, filed Mar. 28, 1991, now U.S. Pat. No. 5,182,040.

FIELD OF THE INVENTION

This invention relates to azeotropic and azeotrope-like mixtures of 1,1,2,2-tetrafluoroethane (HFC-134) and one of 1,1-difluoroethane (HFC-152a), 1-chloro-1,1-difluoroethane (HCFC-142b), 1,1,1,2,3,3,3,-heptafluoropropane (HFC-227ea), perfluorocyclobutane (FC-C318), n-butane or isobutane and their use as refrigerants, aerosol propellants and blowing agents for polymer foams. The azeotropic and azeotrope-like compositions of 1,1,1,2-tetrafluoroethane and one of perfluorocyclobutane and 1,1,1,2,3,3,3-heptafluoropropane are also useful as fire extinguishants. As used herein, extinguishant means the active ingredient used to extinguish fires.

BACKGROUND OF THE INVENTION

The mixtures of the present invention are useful as refrigerants, heat transfer media, gaseous dielectrics, foam expansion agents, aerosol propellants and power cycle working fluids. These mixtures are potentially environmentally safe substitutes for commercial refrigerants such as dichlorodifluoromethane (CFC-12).

Closed-cell polyurethane foams are widely used for insulation purposes in building construction and in the manufacture of energy efficient electrical appliances. In the construction industry, polyurethane (polyisocyanurate) board stock is used in roofing and siding for its insulation and load-carrying capabilities. Poured and sprayed polyurethane foams are also used in construction. Sprayed polyurethane foams are widely used for insulating large structures such as storage tanks, etc. Pour-in-place polyurethane foams are used, for example, in appliances such as refrigerators and freezers, plus they are used in making refrigerated trucks and railcars.

All of these various types of polyurethane foams require expansion agents (blowing agents) for their manufacture. Insulating foams depend on the use of halocarbon blowing agents, not only to foam the polymer, but primarily for their low vapor thermal conductivity, a very important characteristic for insulation value. Historically, polyurethane foams are made with trichlorofluoromethane (CFC-11) as the primary blowing agent.

A second important type of insulating foam is phenolic foam. These foams, which have very attractive flammability characteristics, are generally made with CFC-11 and CFC-113 blowing agents.

A third type of insulating foam is thermoplastic foam, primarily polystyrene foam. Polyolefin foams (polyethylene and polypropylene) are widely used in packaging. These thermoplastic foams are generally made with CFC-12.

Many refrigeration applications, e.g. refrigerators, auto and window air conditioners, etc., presently use CFC-12 as the refrigerant. HFC-134 is a fluorocarbon compound identified as a potential replacement for CFC-12, having properties near those of CFC-12, and being nonflammable with a zero ozone depletion potential. HFC-134 has a thermodynamic refrigeration coefficient of performance somewhat better than that of CFC-12, which may result in energy saving refrigeration applications when HFC-134 is substituted for CFC-12.

Many products designed for household, personal or industrial use are available as aerosol products. Typical examples of such products and ones in which the propellant system of the present invention can be used include personal products such as hair sprays, deodorants and colognes; household products such as waxes, polishes, pan sprays, room fresheners and household insecticides; industrial products such as cleaners, lubricants, and mold release agents; and automotive products such as cleaners and polishes. All such products utilize the pressure of a propellant gas or a mixture of propellant gases (i.e., a propellant gas system) to expel the active ingredients from the container. For this purpose, most aerosols employ liquified gases which vaporize and provide the pressure to propel the active ingredients when the valve on the aerosol container is pressed open.

An important physical property associated with the dispensing of aerosol products is the vapor pressure of the propellant. Vapor pressure from the viewpoint of this invention is the pressure exerted when a liquified propellant gas is in equilibrium with its vapor in a closed container, such as an aerosol can. Vapor pressure can be measured by connecting a pressure gauge to the valve on an aerosol can or gas cylinder containing the vapor/liquid mixture. A standard of measurement of vapor pressure in the U.S. aerosol industry is pounds per square inch gauge (psig) with the gas/liquid mixture at constant temperature, most commonly at 70° F. (21° C.). The vapor pressures of liquified gases most widely employed as aerosol propellants will vary over the range of about 20 to 90 psig (239 to 722 kPa) at 70° F. (21° C.). The propellant systems of the present invention have vapor pressures in this latter range.

In the early 1970s, concern began to be expressed that the stratospheric ozone layer (which provides protection against penetration of the earth's atmosphere by ultraviolet radiation) was being depleted by chlorine atoms introduced to the atmosphere from the release of fully halogenated chlorofluorocarbons. These chlorofluorocarbons are used as propellants in aerosols, as blowing agents for foams, as refrigerants and as cleaning/drying solvent systems. Because of the great chemical stability of fully halogenated chlorofluorocarbons, according to the ozone depletion theory, these compounds do not decompose in the earth's atmosphere but reach the stratosphere where they slowly degrade, liberating chlorine atoms which in turn react with the ozone.

Concern reached such a level that in 1978 the U.S. Environmental Protection Agency (EPA) placed a ban on nonessential uses of fully halogenated chlorofluorocarbons as aerosol propellants. This ban resulted in a dramatic shift in the U.S. away from chlorofluorocarbon propellants (except for exempted uses) to primarily hydrocarbon propellants. However, since the rest of the world did not join the U.S. in this aerosol ban, the net result has been to shift the uses of chlorofluorocarbons in aerosols out of the U.S., but not to permanently reduce the world-wide total chlorofluorocarbon production, as sought. In fact, in the last few years the total amount of chlorofluorocarbons manufactured worldwide has exceeded the level produced in 1978 (before the U.S. ban).

During the period of 1978-1987, much research was conducted to study the ozone depletion theory. Because of the complexity of atmospheric chemistry, many questions relating to this theory remained unanswered. However, assuming the theory to be valid, the health risks which would result from depletion of the ozone layer are significant. This, coupled with the fact that worldwide production of chlorofluorocarbons has increased, has resulted in international efforts to reduce chlorofluorocarbon use. Particularly, in September, 1987, the United Nations through its Environment Programme (UNEP) issued a tentative proposal calling for a 50 percent reduction in worldwide production of fully halogenated chlorofluorocarbons by the year 1998. This proposal was ratified Jan. 1, 1989 and became effective on Jul. 1, 1989.

Because of this proposed reduction in availability of fully halogenal chlorofluorocarbons such as CFC-11, CFC-12 and CFC-113, alternative, more environmentally acceptable, products are urgently needed.

As early as the 1970s with the initial emergence of the ozone depletion theory, it was known that the introduction of hydrogen into previously fully halogenated chlorofluorocarbons markedly reduced the chemical stability of these compounds. Hence, these now destabilized compounds would be expected to degrade in the atmosphere and not reach the stratosphere and the ozone layer. The accompanying Table I lists the ozone depletion potential for a variety of fully and partially halogenated halocarbons. Halocarbon Global Warming Potential data (potential for reflecting infrared radiation (heat) back to earth and thereby raising the earth's surface temperature) are also shown.

                  TABLE I                                                          ______________________________________                                         OZONE DEPLETION AND GREENHOUSE POTENTIALS                                                                   Halocarbon                                                         Ozone Depletion                                                                            Global Warming                                    Blowing Agent    Potential   Potential                                         ______________________________________                                         CFC-11 (CFCl.sub.3)                                                                             1.0         1.0                                               CFC-12 (CF.sub.2 Cl.sub.2)                                                                      1.0         3.1                                               HCFC-22 (CHF.sub.2 Cl)                                                                          0.05        0.34                                              HCFC-123 (CF.sub.3 CHCl.sub.2)                                                                  0.02        0.02                                              HCFC-124 (CF.sub.3 CHFCl)                                                                       0.02        0.1                                               HFC-134a (CF.sub.3 CH.sub.2 F)                                                                  0.          0.28                                              HFC-134 (CHF.sub.2 CHF.sub.2)                                                                   0.          0.3                                                                            (est.)                                            HCFC-141b (CFCl.sub.2 CH.sub.3)                                                                 0.15        0.15                                              HCFC-142b (CF.sub.2 ClCH.sub.3)                                                                 0.06        0.36                                              HFC-152a (CHF.sub.2 CH.sub.3)                                                                   0.          0.03                                              CFC-113 (CF.sub.2 Cl--CFCl.sub.2)                                                               0.8         1.4                                               FC-C318 (CF.sub.2 --CF.sub.2) (CF.sub.2 --CF.sub.2)                                             0.          Not available                                     HFC-227ea (CF.sub.3 CHFCF.sub.3)                                                                0           Not available                                     ______________________________________                                    

Halocarbons such as HFC-134, HFC-152a, HFC-227ea and FC-C318 have zero ozone depletion potential. N-butane and isobutane, having no halogen content, are also zero ozone depleters. HCFC-142b has an ozone depletion potential of 0.06.

Although 1,1,2,2-tetrafluoroethane has utility as a refrigerant, aerosol propellant or foam blowing agent, azeotropes offer the possibility of producing more economical nonfractionating systems with improved properties such as refrigeration performance, polymer and refrigerant oil solubility.

Unfortunately, as recognized in the art, it is not possible to predict the formation of azeotropes.

This fact obviously complicates the search for new azeotropes which have application in the field. Nevertheless, there is a constant effort in the art to discover new azeotropic compositions, which have desirable characteristics.

SUMMARY OF THE INVENTION

In accordance with the present invention, azeotropic or azeotrope-like mixtures have been discovered, which comprise effective amounts of 1,1,2,2-tetrafluoroethane (HFC-134) and one of 1,1-difluoroethane (HFC-152a), 1-chloro-1,1-difluoroethane (HCFC-142b), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), perfluorocyclobutane (FC-C318), n-butane or isobutane.

In accordance with the present invention, azeotropic or azeotrope-like mixtures have been discovered, which consist essentially of effective amounts of 1,1,2,2-tetrafluoroethane (HFC-134) and one of 1,1-difluoroethane (HFC-152a), 1-chloro-1,1-difluoroethane (HCFC-142b), 1,1,1,2,3,3,3-heptafluoropropane HFC-227ea, perfluorocyclobutane (FC-C318), n-butane or isobutane, preferably the azeotropic mixture of HFC-134 and 1 to 20 weight percent of HFC-152a.

The azeotropes of HFC-134 and one of HCFC-142b, n-butane, HFC-227ea, isobutane and FC-C318 are minimum boiling azeotropes; thus, the vapor pressure is higher and the boiling point lower for the azeotropes than for the components. The azeotrope of HFC-134 and HFC-152a is a maximum boiling azeotrope; thus, the vapor pressure is lower and the boiling point higher for the azeotrope than for the components.

DETAILED DESCRIPTION OF THE INVENTION

The novel azeotropic or azeotrope-like compositions of the invention were discovered during a phase study wherein the compositions were varied and vapor pressures measured. By this procedure the following azeotropic compositions reported in Table II were discovered:

                  TABLE II                                                         ______________________________________                                                                            Vapor                                                                          Pressure,                                   Components   Composition*                                                                               Temp. °C.                                                                         psia (kPa)                                  ______________________________________                                         HFC-134/HFC-152a                                                                            92.0/8.0    10        46.5 (321)                                  HFC-134/HCFC-142b                                                                           95.9/4.1    -17       16.6 (114)                                  HFC-134/FC-C318                                                                             62.3/37.7    0        36.9 (254)                                  HFC-134/n-butane                                                                            83.1/16.9   10        56.9 (392)                                  HFC-134/isobutane                                                                           76.7/23.3   10        63.5 (438)                                  HFC-134/HFC-227ea                                                                           52.0/48.0   -10       23.5 (162)                                  ______________________________________                                          *All compositions are ± 2 wt. percent.                                

    Atmospheric Boiling Points of Components, °C.                           ______________________________________                                         HFC-134     -19.5     n-butane     -0.5                                        HFC-152a    -25.0     Isobutane    -11.7                                       HCFC-142b   -9.8      HFC-227ea    -18.0                                       FC-C318     -6.1                                                               ______________________________________                                    

For the purpose of this discussion, azeotropic, azeotropic-like or constant boiling is intended to mean also essentially azeotropic or essentially constant boiling. In other words, included within the meaning of these terms are not only the true azeotrope described above, but also other compositions containing effective amount of the same components in somewhat different proportions, which are true azeotropes at other temperatures and pressures, as well as those equivalent compositions which are part of the same azeotropic system and are azeotropic in their properties. As is well recognized in this art, there is a range of compositions which contain the same components as the azeotrope, which not only will exhibit essentially equivalent properties for refrigeration and other applications, but which will also exhibit essentially equivalent properties to the true azeotropic composition in terms of constant boiling characteristics or tendency not to segregate or fractionate on boiling.

It is possible to characterize, in effect, a constant boiling admixture, which may appear under many guises, depending upon the conditions chosen, by any of several criteria:

The composition can be defined as an azeotrope of A and B since the very term "azeotrope" is at once both definitive and limitative, and requires that effective amounts of A and B form this unique composition of matter, which is a constant boiling admixture at a given pressure.

It is well known by those skilled in the art that at different pressures, the composition of a given azeotrope will vary--at least to some degree--and changes in pressure will also change--at least to some degree the boiling temperature. Thus, an azeotrope of A and B represents a unique type of relationship but with a variable composition which depends on temperature and/or pressure. Therefore, compositional ranges, rather than fixed compositions are often used to define azeotropes.

The composition can be defined as a particular weight percent relationship or mole percent relationship of A and B while recognizing that such specific values point out only one particular such relationship and that in actuality, a series of such relationships, represented by A and B actually exist for a given azeotrope, varied by the influence of pressure.

Azeotrope A and B can be characterized by defining the composition as an azeotrope characterized by a boiling point at a given pressure, thus giving identifying characteristics without unduly limiting the scope of the invention by a specific numerical composition, which is limited by and is only as accurate as the analytical equipment available.

It is recognized in the art that the difference between dew point temperature and bubble point temperature is an indication of the constant boiling or azeotrope-like behavior of mixtures. It has been unexpectedly found that compositions some distance away from the azeotrope compositions of this invention have differences in dew point/bubble point temperatures of less than or equal to one degree Celsius. The small temperatures differentials demonstrated by these compositions are less than values for azeotrope-like ternary mixture of HCFC-22, HFC-152a, and HCFC-124 described in U.S. Pat. No. 4,810,403.

Therefore, included in this invention are the azeotrope-like compositions having dew point/bubble point differences of less than or equal to one degree Celsius reported in Table III. These data confirm the azeotrope-like behavior of the compositions claimed in this invention. The value for the ternary mixture of U.S. Pat. No. 4,810,403 is shown for comparison.

                  TABLE III                                                        ______________________________________                                                                   Maximum Difference                                                             In Dew Point/Bubble                                  Components   Composition* Point Temp., °C.                              ______________________________________                                         HCFC-22/HFC-152a/                                                                           36/24/40     5.3                                                  HCFC-124                                                                       HFC-134/HFC-152a                                                                            1-20% HFC-152a                                                                              0.0                                                  HFC-134/HCFC-142b                                                                           1-10% HFC-142b                                                                              0.0                                                  HFC-134/HCFC-142b                                                                           1-40% HFC-142b                                                                              0.8                                                  HFC-134/DME  1-40% DME    0.7                                                  HFC-134/FC-C318                                                                             1-50% FC-C318                                                                               1.0                                                  HFC-134/n-butane                                                                            1-20% n-butane                                                                              0.7                                                  HFC-134/iso-butane                                                                          1-30% iso-butane                                                                            0.7                                                  HFC-134/HFC-227ea                                                                           1-99% HFC-227ea                                                                             0.8                                                  ______________________________________                                          *weight percent; 14.7 psia pressure.                                     

Most preferred compositions of this invention are the azeotropic compositions having dew point/bubble point differences of less than or equal to 0.1 degree Celsius as reported for HFC-134/HFC-152a in Table 3 and for such compositions containing about 80-99 weight percent HFC-134 and about 1-20 weight percent HFC-152a.

The azeotropic and azeotrope-like compositions of the invention are useful as refrigerants, expansion agents and as aerosol propellants, among other applications. The azeotropic and azeotrope-like compositions of 1,1,1,2-tetrafluoroethane and one of perfluorocyclobutane and 1,1,1,2,3,3,3-heptafluoropropane are also useful as fire extinguishants.

Mixtures of HFC-134, HFC-227ea, and FC-C318 are nonflammable. The azeotropes of HFC-134 and HFC-152a or HCFC-142b are also nonflammable. Additionally, mixtures of HFC-134 and n-butane, or isobutane can be formulated such that they are nonflammable. Therefore, the azeotropic compositions of HFC-134, n-butane, or isobutane are of significantly reduced flammability compared with n-butane, or isobutane alone.

Another aspect of the invention is a refrigeration method which comprises condensing a refrigerant composition of the invention and thereafter evaporating it in the vicinity of a body to be cooled. Similarly, still another aspect of the invention is a method for heating which comprises condensing the invention refrigerant in the vicinity of a body to be heated and thereafter evaporating the refrigerant.

In the heating and cooling applications, the nonflammable compositions are particularly useful.

These azeotropic and azeotrope-like compositions are useful as propellants for aerosol sprays, e.g., room fresheners. The azeotropes are particularly attractive as they do not separate or fractionate when used in aerosol packages equipped with vapor tap valves wherein the propellant is removed, at least partially, vapor phase.

The binary refrigerant compositions of the invention are useful in compression cycle applications including air conditioner and heat pump systems for producing both cooling and heating. The new refrigerant mixtures can be used in refrigeration applications as described in U.S. Pat. No. 4,482,465 to Gray, which patent is incorporated herein by reference.

The language "consisting essentially of 1,1,2,2-tetrafluoroethane" is not intended to exclude the inclusion of minor amounts of other materials such as lubricants and stabilizers which do not significantly alter the azeotropic character of the azeotropic composition.

The compositions of the instant invention can be prepared by any convenient method including mixing or combining, by other suitable methods, the desired amounts of the components, using techniques well-known to the art.

Specific examples illustrating the invention are given below. Unless otherwise stated therein, all percentages are by weight. It is to be understood that these examples are merely illustrative and in no way to be interpreted as limiting the scope of the invention.

EXAMPLE 1

A phase study was made on 1,1,2,2-tetrafluoroethane (HFC-134) and HFC-152a, HCFC-142b, HFC-227ea, FC-C318, n-butane, and isobutane, respectively, wherein the compositions were varied and the vapor pressures measured. The following azeotropic compositions reported in Table IV were defined:

                  TABLE IV                                                         ______________________________________                                                                          Vapor Pressure,                               Components  Composition*                                                                              Temp. °C.                                                                         psia (kPa)                                    ______________________________________                                         HFC-134/HFC-152a                                                                           92.0/8.0   10        46.5 (321)                                    HFC-134/HCFC-142b                                                                          95.9/4.1   -17       16.6 (114)                                    HFC-134/FC-C318                                                                            62.3/37.7   0        36.9 (254)                                    HFC-134/n-butane                                                                           83.1/16.9  10        56.9 (392)                                    HFC-134/isobutane                                                                          76.7/23.3  10        63.5 (438)                                    HFC-134/HFC-227ea                                                                          52.0/48.0  -10       23.5 (162)                                    ______________________________________                                          *All compositions are ± 2 wt. percent.                                

EXAMPLE 2

A determination was made of dew point and bubble point temperatures for the mixtures of the invention, shown in Table V. All have temperature differentials of less than or equal to one degree Celsius.

                  TABLE V                                                          ______________________________________                                                     Temperature, °C. at 14.7 psia                               Composition, wt %                                                                            Dew Point Bubble Point                                                                              Difference                                  ______________________________________                                         HFC-134/HFC-152a                                                               99      1         -19.6     -19.6    0.0                                       92      8         -19.5     -19.5    0.0                                       90      10        -19.5     -19.5    0.0                                       80      20        -19.7     -19.7    0.0                                       HFC-134/HCFC-142b                                                              99      1         -19.6     -19.6    0.0                                       95.9    4.1       -19.7     -19.7    0.0                                       90      10        -19.6     -19.6    0.0                                       70      30        -18.4     -18.9    0.5                                       60      40        -17.4     -18.2    0.8                                       HFC-134/FC-C318                                                                99      1         -20.3     -19.9    0.4                                       95      5         -21.6     -20.6    1.0                                       90      10        -22.1     -21.2    0.9                                       70      30        -22.0     -22.2    0.2                                       62.3    37.7      -22.2     -22.2    0.0                                       60      40        -22.2     -22.2    0.0                                       50      50        -21.1     -22.1    1.0                                       HFC-134/n-butane                                                               95      5         -24.6     -24.0    0.6                                       90      10        -24.4     -24.5    0.1                                       83.1    16.9      -24.6     -24.6    0.0                                       80      20        -23.9     -24.9    0.7                                       HFC-134/iso-butane                                                             95      5         -27.4     -26.8    0.6                                       90      10        -27.8     -27.5    0.3                                       80      20        -27.8     -27.8    0.0                                       76.7    23.3      -27.7     -27.7    0.0                                       70      30        -27.1     -27.8    0.7                                       HFC-134/HFC-227ea                                                              99      1         -19.7     -19.7    0.0                                       95      5         -19.8     -19.9    0.1                                       90      10        -20.0     -20.2    0.2                                       70      30        -20.8     -20.9    0.1                                       52      48        -21.1     -21.1    0.0                                       30      70        -20.3     -20.6    0.3                                       10      90        -18.0     -18.8    0.8                                       5       95        -17.2     -17.8    0.6                                       1       99        -16.5     -16.7    0.2                                       ______________________________________                                    

EXAMPLE 3

An evaluation of the refrigeration properties of the mixtures of the invention versus dichlorodifluoromethane (CFC-12) and 1,1,2,2-tetrafluoroethane (HFC-134), respectively, are shown in following Table VI. The data were generated on a one ton basis, that is to say, on the removal of heat from a space at the rate of 12,000 Btu/hr (3516 watts). The data are based on the ideal refrigeration cycle.

                                      TABLE VI                                     __________________________________________________________________________     COMPARISON OF REFRIGERATION PERFORMANCES                                       __________________________________________________________________________                               Weight Percentages                                                                                62% HFC-134                                                 CFC-12   HFC-134   38% C318                          __________________________________________________________________________     Evaporator                                                                     Temp.,          °F.                                                                               0        0         0                                                 (°C.)                                                                             (-17.7)  (-17.7)   (-17.7)                           Press.          psia      23.8     15.9      18.2                                              (kPa)     (164.)   (110.)    (125.)                            Condenser                                                                      Temp.,          °F.                                                                               130      130       130                                               (°C.)                                                                             (54.4)   (54.4)    (54.4)                            Press.          psia      195.7    170.5     181.8                                             (kPa)     (1349.)  (1175.)   (1253.)                           Superheat, °F.     90       90        90                                Subcool, °F.       40       40        40                                Coefficient of Performance                                                                               2.42     2.50      2.36                              Displacement ft.sup.3 /min/ton                                                                           8.1      10.4      10.3                              __________________________________________________________________________                 Weight Percentages                                                             90% HFC-134                                                                           75% HFC-134                                                                            90% HFC-134                                                                            52% HFC-134                                                                            83% HFC-134                                                                           77% HFC-134                              10% HFC-152a                                                                          25% HCFC-142b                                                                          10% HCFC-142b                                                                          48% HFC-227ea                                                                          17% n-butane                                                                          23% isobutane                __________________________________________________________________________     Evaporator                                                                     Temp.,                                                                               °F.                                                                           0      0       0       0       0      0                                  (°C.)                                                                         (-17.7)                                                                               (-17.7) (17.7)  (17.7)  (17.7) (17.7)                       Press.                                                                               psia  16.0   15.4    15.8    17.5    12.8   14.4                         Condenser                                                                      Temp.,                                                                               °F.                                                                           130    130     130     130     130    130                                (°C.)                                                                         (54.4) (54.4)  (54.4)  (54.4)  (54.4) (54.4)                       Press.                                                                               psia  169.7  161.4   167.3   178.6   141.1  148.5                              (kPa) (1170.)                                                                               (1113.) (1153.) (1232)  (974)  (1025)                       Superheat, °F.                                                                      90     90      90      90      90     90                           Subcool, °F.                                                                        40     40      40      40      40     40                           Coefficient of Performance                                                                 2.51   2.49    2.50    2.34    2.50   2.47                         Displacement ft.sup.3 /min/ton                                                             10.3   10.9    10.5    10.7    12.9   12.0                         __________________________________________________________________________

Coefficient of Performance (COP) is a measure of refrigerant energy efficiency.

Additives such as lubricants, corrosion inhibitors, stabilizers, dyes and other appropriate materials may be added to the novel compositions of the invention for a variety of purposes provided they do not have an adverse influence on the composition, for their intended applications.

EXAMPLE 4

Aerosol room fresheners were prepared with the azeotropes of HFC-134 with HFC-152a, HCFC-142b, DME, FC-C318, n-butane and isobutane. The formulations and vapor pressures are reported in Table VII.

                  TABLE VII                                                        ______________________________________                                         AEROSOL ROOM FRESHENER FORMULATION                                                        Wt. %                                                               Ingredient   1       2       3     4     5                                     ______________________________________                                         Perfume      2.0     2.0     2.0   2.0   2.0                                   Propellant*  98.0A   98.0B   98.0C 98.0D 98.0E                                 Vapor Pressure at 70° F.,                                                            55      54      74.5  69    76                                    psig                                                                           (21° C., kPa)                                                                        (481)   (474)   (615) (578) (626)                                 ______________________________________                                          *Propellants                                                                   A  HFC134/HFC-152a (97.4/2.6)                                                  B  HFC134/HCFC-142b (96.8/3.2)                                                 C  HFC134/FC-C318 (62.1/37.9)                                                  D  HFC134/n-butane (82.5/17.5)                                                 E  HFC134/isobutane (74.0/26.0)                                          

EXAMPLE 5

The solubilities of the HFC-134 azeotropes were determined in a polyurethane polyol. The azeotropes of HFC-134 with HFC-152a, HCFC-142b, n-butane and isobutane were readily soluble at 30.0 wt. % in the polyol, as was HFC-134 itself. The solubility data are summarized in Table VIII.

                  TABLE VIII                                                       ______________________________________                                         SOLUBILITY OF HFC-134/DIMETHYL ETHER AZEOTROPE                                 IN POLYOL                                                                      Blowing Agent                                                                               Wt. % in Polyol*                                                                            Appearance                                           ______________________________________                                         HFC-134      30.0         Soluble, single phase                                HFC-134/HFC-152a                                                                            30.0         Soluble, single phase                                (97.4/2.6)                                                                     HFC-134/HCFC-142b                                                                           30.0         Soluble, single phase                                (96.8/3.2)                                                                     HFC-134/n-butane                                                                            30.0         Soluble, single phase                                (82.5/17.5)                                                                    HFC-134/isobutane                                                                           30.0         Soluble, single phase                                (74.0/26.0)                                                                    ______________________________________                                          *Stepanpol PS2852 (Stepan Company), an aromatic polyester polyol.        

EXAMPLE 6

The solubility of the HFC-134 azeotropes in polystyrene was determined by combining a piece of polystyrene (about 2.5 cm long, 0.5 g cm wide and 0.5 cm thick) with about 50 g. azeotrope. Only the HFC-134/n-butane (82.5/17.5) azeotrope had any appreciable solubility in polystyrene, softening and deforming the piece of polystyrene. The data are summarized in Table IX.

                  TABLE IX                                                         ______________________________________                                         SOLUBILITY OF HFC-134 AZEOTROPES IN POLYSTYRENE                                Blowing Agent  Appearance of Polystyrene                                       ______________________________________                                         HFC-134        Essentially no effect                                           HFC-134/HFC-152a                                                                              Essentially no effect                                           (97.4/2.6)                                                                     HFC-134/HCFC-142b                                                                             Essentially no effect                                           (96.8/3.2)                                                                     HFC-134/FC-C318                                                                               Essentially no effect                                           (62.1/37.9)                                                                    HFC-134/n-butane                                                                              Polystyrene softened and deformed*                              (82.5/17.5)                                                                    HFC-134/isobutane                                                                             Essentially no effect                                           (74.0/26.0)                                                                    ______________________________________                                          *On removing the polystyrene from the azeotrope, expansion occurred from       solubilized HFC134.                                                      

EXAMPLE 7

A determination was made at dew point and bubble point temperatures for mixtures of 1,1,2,2-tetrafluoroethane (HFC-134) and HFC-152a to determine the azeotropic composition range, i.e., where the temperature differential is less than 0.1 degree Celsius.

                  TABLE X                                                          ______________________________________                                         Composition. wt. %                                                                           Temperature °C. at 14.7 psia.                             HFC-134/HFC-152a                                                                             Bubble Pt. Dew Pt. Difference                                    ______________________________________                                         30        70      -22.83     -22.3 0.53                                        40        60      -22.15     -21.63                                                                               0.52                                        50        50      -21.46     -21   0.46                                          54.7*     45.3  -21.13     -20.74                                                                               0.39                                        60        40      -20.78     -20.45                                                                               0.33                                        70        30      -20.16     -19.99                                                                               0.17                                        75        25      -19.9      -19.8 0.1                                         80        20      -19.7      -19.65                                                                               0.05                                        90        10      -19.5      -19.5 0                                           92         8      -19.5      -19.5 0                                           99         1      -19.6      -19.6 0                                           ______________________________________                                          *Composition disclosed in Bailey U.S. Pat. No. 3,732,150.                 

We claim:
 1. An azeotropic composition consisting essentially of about 80-99 weight percent 1,1,2,2-tetrafluoroethane and about 1-20 weight percent 1,1-difluoroethane, wherein the dew point and the bubble point are both about -19.6° C. at 14.7 psia.
 2. An azeotropic composition consisting essentially of about 92 weight percent 1,1,2,2-tetrafluoroethane and about 8 weight percent 1,1-difluoroethane wherein the dew point and the bubble point are both about -19.6° C. at 14.7 psia, said composition having a boiling temperature of about 10 degrees C. when the pressure is adjusted to about 46 psia.
 3. A process of producing refrigeration which comprises condensing the azeotropic composition of claim 1 and thereafter evaporating said composition in the vicinity of a body to be cooled.
 4. An aerosol propellant composition consisting essentially of the azeotropic composition of claim
 1. 5. The aerosol propellant composition of claim 4 consisting essentially of about 97.4 weight percent 1,1,2,2-tetrafluoroethane and about 2.6 weight percent difluoroethane. 